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Suppose the observed Wilcoxon-Mann-Whitney (WMW) test-statistics Uobs is the smaller
of the two calculated rank-sum values (U1 and U2). If
Uobs < Ucritical, which is reported in the table below for
different combinations of sample-sizes (N1 and N2) and false-positive rates
(α), then we would reject the null hypothesis Ho of no group differences
bwtween the two samples. For sample sizes (N1 & N2) larger than 20 use
Normal Approximation and the Standard Normal Table
to calculate critical values. You can also use the diverse
SOCR Distirbutions and
SOCR Analyses applets to compute accurate estimates of
critical-values and p-values. See
detailed description and examples on the SOCR SMHS EBook site.